Grommets of the type with which the present invention is concerned are adapted to be mounted and retained within a panel or wall opening. As so mounted, such grommets are also intended to support means such as wires, conduits, or cables which extend through the wall or panel but are maintained out of contact therewith by the grommet. Grommets of this general type are shown in U.S. Pat. Nos. Re. 26,740; 3,182,119; 3,182,120; and 3,654,382. As shown in the aforementioned patents, it is also necessary with this type of grommet to provide suitable means to snap in or otherwise retain the grommet within the panel opening. Accordingly, it has been common practice to form such grommets of an elastomeric material within which a non-elastomeric retaining member or ring is at least partially imbedded so as to present locking fingers or tangs which coact with the panel opening to lock the grommet therewithin.
In certain environments such as in automobiles where grommets are commonly used in the wall or panel between the passenger and engine compartments, it is not only necessary but presently mandated by law that such grommets seal the panel openings so as to prevent the flow of liquids or gases therethrough. Thus, the grommet of the type shown in aforementioned U.S. Pat. No. 3,654,382 is particularly designed and directed to include a sealing function.
The present invention is an improvement over such earlier types of sealing grommets and particularly includes a unique monolithic elastomeric body design wherein a panel opening is more effectively sealed against the flow of gases or liquids therethrough and, further, in which the non-elastomeric locking element is essentially entirely imbedded in the body in such a way as to avoid undesired exposure of the locking element and preventing any contact therewith by the wire, cable, conduit, or the like, supported by the grommet or any other member otherwise proximate to the panel opening.
Another problem with heretofore known types of grommets has been their general inability to properly seal an opening where it is formed in a curved or arcuate panel surface. For example, while a grommet such as that shown in U.S. Pat. No. 3,654,382 effectively seals an opening in a flat panel section, it provides a less effective seal where the panel is of a curved cross-section. The problem in sealing against an arcuate surface with heretofore known types of grommets basically relates to the use of a single planar elastomeric sealing surface. In such case an annular lip or edge is compressed against the panel surface to be sealed and retained in such position by the grommet locking means. As the panel surface becomes curved or arcuate in cross-section, the panel surface, in effect, either moves away from the sealing edge of the grommet when the grommet is mounted on the convex side of the curve, or moves toward the sealing edge when the grommet is mounted on the concave side of the curve. In either event and since the curved panel is normally the section of a cylinder, a gap results at some point between the grommet sealing edge and the panel surface which thereby prevents effective sealing. If one attempts to obviate the gapping problem by increasing or decreasing the size or thickness of the sealing lip or edge, then it becomes difficult, if not impossible, to compress the lip sufficiently to permit adequate locking engagement between the locking tangs and the panel opening.
The sealing grommet of the present invention is uniquely adapted to seal an opening in either a flat or a curved panel by not only providing a first planar elastomeric surface which coacts with the panel surface surrounding the panel opening but by also providing a second annular elastomeric sealing surface which coacts with the panel opening itself to insure a proper seal by the grommet.